In known knitting methods successive stitches or loops are formed and interlaced by means of needles which may or may not be provided with latches. These needles are mounted in a row in a cylinder of a circular knitting machine or a needle bed of a flat knitting machine. In the lattery type of machine the needle support is an elongated element provided with an array of parallel needle seats extending perpendicular to the longitudinal direction of the element. In circular knitting machines the needle support is provided on its periphery with an array of parallel needle seats corresponding to generatrices of the cylinder. In both cases the needles are displaced longitudinally of their seats. With each reciprocal movement each needle slides along a stitch or loop which it has just formed and hooks on a thread or filament which is to form the next stitch or loop, returning backwardly with the previous stitch sliding off the tip of the needle around the thread that was just picked up. A loop of this thread is thus pulled through the loop already around the needle and the previously formed loop slides off the needle around the newly formed loop.
The reciprocal movements of the needles are effected by means of fixed or movable cams. In circular machines the cams can be fixed in which case the cylinder turns around its axis, or movable in which case the cylinder is fixed. In flat-bed machines the cams are always carried by a carriage which is displaced along the needle support.
These machines, although they produce perfectly usable knitted goods, are relatively complicated and very expensive. The needles must be extremely carefully machined in order not to catch on the stitches, and the joints of their latches, where provided, must have a very exactly controlled play. The body of the needles must have thicknesses which are extremely regular in order to slide freely, but must not slide in their seats with excessive play. The seats of the needles in addition must be machined with a great deal of precision.
Furthermore controlling the reciprocal movement of the needles creates considerably problems of acceleration. Retaining the needles in place is difficult and the risk of breaking the filament can only be decreased by slowing down the working speed, which, therefore, increases product cost. Another considerable disadvantage is that the extremely complicated knitting machines are typically only usable for a particular cut, that is wales per inch, so that a great deal of equipment is necessary to produce different kinds of goods.